Integrated ball screw linear actuator

ABSTRACT

A linear actuation screw having a first end portion, a second end portion on an opposite side as the first end portion, and a sloping intermediate portion between the first end portion and second end portion. The first end portion has a threaded outer wall having a generally constant first diameter over at least a portion of its length and is configured to advance a nut or a sliding member along at least a portion of the first end portion. The second end portion has a threaded outer wall having a generally constant second diameter that is different from the first diameter and is configured to receive a motor fastening nut around it in order to secure the linear actuation screw to a motor. The sloping intermediate portion includes an outer wall that is generally smooth and continuous over at least a majority of the area of the outer wall.

FIELD

In general, the present teachings relate to an improved linear actuationscrew for use in a linear actuator, and particularly to a ball screw andthat directly connects to a motor in a linear actuation system.

BACKGROUND

It is common in the linear actuator field to employ a threaded screwthat is rotated (e.g., by a motor) for causing a linear guide totranslate along the length of the threaded screw. Essentially a rotarymotion of the screw is converted to a linear motion of the linear guide.For this purpose, it has been common to employ a ball recirculationsystem for facilitating the actuation.

Common linear actuator systems include a screw shaft which is supportedby rolling bearings in an intermediate support unit, a screw nut, alinear sliding part which is combined with the screw nut, a linear rail,a support unit, a rotary motor, a motor bracket, and a coupling forconnecting the screw shaft and a shaft of the motor. This common systemhas three rotational parts: the shaft in the motor, the shaft of thescrew, and the coupling. The intermediate support unit also haspreloaded bearings which support screw shaft rotation movement.

Notwithstanding efforts over the years to improve linear actuators,there still remains a need for simplifying the design and more easilyand accurately connecting the screw to the motor. There also remains aneed for reducing the footprint of the linear actuator. There furtherremains a need for decreasing assembly time by reducing the number ofparts. There is also a need for reducing or eliminating misalignmentbetween the coupling, the screw shaft, and the motor rotation shaft.

The following U.S. patent document may be related to the presentteachings: U.S. Pat. No. 3,192,791, all of which is incorporated byreference herein for all purposes. Also potentially related to thepresent teachings is a product available commercially from NSK Ltd.under the name “Monocarrie™”, which is a linear motion product thatincludes a ball screw, a linear rail and a slider that is slidinglyattached to the rail.

SUMMARY

The present teachings make use of a simple, yet elegant, approach to theconstruction of an improved linear actuation screw (e.g., for animproved linear actuator). A linear actuator employing the linearactuation screw of the present teachings may have a driver (e.g., amotor) that mates directly with the screw. The screw may have at leastone helical thread (e.g., having generally opposing flanks) and alongitudinal axis. The screw may be coupled with the driver (e.g.,motor) and in driving relationship with the motor so the motor isadapted to rotate the screw generally about the longitudinal axis of thescrew. The linear actuator may include a slider assembly which may beconfigured for linear translation along the longitudinal axis of thescrew.

In accordance with the present teachings, there is thus contemplated alinear actuation screw. The linear actuation screw may include anelongated shaft having a first end portion, a second end portion on anopposite side of the elongated shaft as the first end portion, and asloping intermediate portion between the first end portion and thesecond end portion. The first end portion may have a threaded outer wallhaving a generally constant first diameter (as measured from a crest)over at least a portion of its length. The first end portion may beconfigured to advance a nut or a sliding member along at least a portionof the first end portion. The second portion may have a threaded outerwall having a generally constant second diameter (e.g., a diameter thatis different from the first diameter). The second end portion may beconfigured to receive a motor fastening nut around it in order to securethe linear actuation screw to a motor. The sloping intermediate portionmay include an outer wall that is generally smooth and continuous overat least a majority of the area of the outer wall. The linear actuationscrew may be a ball screw.

The first diameter of the threaded outer wall of the first end portion,the second diameter of the threaded outer wall of the second endportion, or both, may be generally constant over substantially theentire length of the first end portion, the second end portion, or both.The first diameter of the threaded outer wall of the first end portion,the second diameter of the threaded outer wall of the second endportion, or both, may be generally constant over only a portion of thelength of the first end portion, the second end portion, or both. Theaverage first diameter of the first end portion (as measured from atrough), or the minor diameter of the first end portion, may bedifferent from an average second diameter of the second end portion (asmeasured from a trough), or the minor diameter of the second endportion. A portion of the first end portion may have a differentdiameter than the first diameter of the first end portion. The differentdiameter portion may be adapted to be supported by a carriage of alinear actuator.

The threaded outer wall of the first end portion, the threaded outerwall of the second end portion, or both, may be threaded over only aportion of the first end portion, the second end portion, or both. Thethreaded outer wall of the first end portion, the threaded outer wall ofthe second end portion, or both, may be threaded over greater than 50percent of the length of the first end portion, the second end portion,or both. The threaded outer wall of the first end portion, the threadedouter wall of the second end portion, or both, may be threaded oversubstantially the entire first end portion, the second end portion, orboth. There may be a portion that is unthreaded between the first endportion and the second end portion.

The sloping intermediate portion may have a slope between about 5degrees and about 10 degrees relative to a longitudinal axis of thelinear actuation screw. The sloping intermediate portion may have agenerally constant slope over a majority of its length. A ratio of thelength of the second end portion to a length of the sloping intermediateportion may be about 3.3:1 to about 0.7:1.

The linear actuation screw may be adapted to penetrate at leastpartially through a through passage of a motor and be secured. The motormay include an encoder. An encoder journal may be located at and extendfrom the second end portion of the linear actuation screw along thelongitudinal axis of the linear actuation screw for receipt within theencoder.

The present teachings also contemplate an assembly including the linearactuation screw and a motor fastening nut.

The present teachings further contemplate a method of assembling amotorized assembly including the linear actuation screw as disclosedherein. The method may include: providing a motor having a first endportion, a second end portion, and a through passage through which thelinear actuation screw at least partially penetrates; inserting thelinear actuation screw at least partially into the through passage fromthe first end portion of the motor; and securing the linear actuationscrew within the motor by threadingly engaging the motor fastening nutonto the second end portion of the linear actuation screw. The slopingintermediate portion of the linear actuation screw may matingly engage awall that defines the through passage. Upon securing the linearactuation screw within the motor by threadingly engaging the motorfastening nut onto the second end portion of the linear actuation screw,the motor may require no further assembly steps for operation.

The first end portion of the motor may include a motor plate for atleast partially enclosing the motor. The linear actuation screw may beinserted so that the sloping intermediate portion is longitudinallyspaced within the motor at a distance of at least 3 mm from an outerwall of the motor plate. It is possible that the space between thesloping intermediate, portion and the outer wall of the motor plate maybe no greater than a total length of the sloping intermediate portion. Amotor cover plate structure may be added on the second end portion ofthe motor. An encoder may be added on the second end portion of themotor.

At least a portion of the linear actuation screw may be exposed duringoperation of the motor. A substantial portion (e.g., a majority) of thefirst end portion of the linear actuation screw may be located externalof the motor. A substantial portion (e.g., a majority) of the first endportion may be free of any enclosure. The motorized assembly may be freeof an adapter or coupling joining the linear actuation screw and themotor.

The present teachings also contemplate an actuator assembly including:the linear actuation screw; a carrier that carries the linear actuationscrew; a motor that drives rotation of the linear actuation screw; and alinear slider for translating fore and aft along an axis that isgenerally parallel to the longitudinal axis of the linear actuationscrew. The carrier may include a first end portion and a second endportion. The first end portion may have at least one end bearing. Thefirst end portion of the carrier may support the first end portion ofthe linear actuation screw. The second end portion of the carrier mayinclude the motor. The second end portion of the linear actuation screwmay be attached directly to the motor and penetrate at least partiallyinto the motor. The carrier may include a linear rail upon which thelinear slider translates fore and aft.

The actuator assembly may be free of an intermediate support unitbetween the motor and the at least one end bearing (or the first endportion of the carrier). The assembly may be free of a motor bracket.The assembly may be free of an adapter or coupling (e.g., for joiningthe linear actuation screw to a motor shaft). The carrier may have anoverall length, and the linear actuation screw may a travel length overthe distance which a screw nut located on the linear actuation screw cantravel. A ratio of the overall length of the carrier to the travellength of the linear actuation screw may be about 1.4:1 or less (e.g.,about 1.3:1 or less). The actuator assembly may result in a reduction ofoverall length of at least 15%, at least 20%, or more, as compared witha traditional structure having an intermediate support unit.

The present teachings provide a number of technical benefits, includingbut not limited to, providing a screw that directly mates with a motorfor eliminating the need for a coupling between the screw shaft and amotor shaft, reducing the footprint of an assembled linear actuatorassembly, reducing the number of parts needed (e.g., by reducing oreliminating the need for an intermediate support unit containing one ormore rolling bearings), or any combination of the foregoing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a traditional linear actuator assembly.

FIG. 2 illustrates a motorized assembly including a linear actuationscrew of the present teachings.

FIGS. 3A and 3B is a side view of a partial linear actuation screw ofthe present teachings.

FIG. 4 is a partial cutaway view of a portion of the linear actuationscrew of the present teachings received within a motor.

FIG. 5 illustrates a longitudinal cross section of a linear actuationscrew of the present teachings having a sloping intermediate portion byway of a tapered adapter.

FIG. 6A illustrates a motorized assembly including a linear actuationscrew of the present teachings including an encoder journal extendingtherefrom.

FIG. 6B illustrates the linear actuation screw of FIG. 6A with the motoromitted.

FIG. 6C illustrates a motorized assembly including a linear actuationscrew of the present teachings and an encoder attached to the motor.

FIG. 7 illustrates an actuator assembly including the linear actuationscrew of the present teachings.

DETAILED DESCRIPTION

As required, details of the present teachings are disclosed herein;however, it is to be understood that the disclosed teachings are merelyexemplary of the teachings that may be embodied in various andalternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

In general, and as will be appreciated from the description thatfollows, the present teachings pertain to a simple, yet elegant,approach to the construction of an improved linear actuation screw whichmay be employed within a linear actuator. The present teachings alsopertain to an improved linear actuation assembly where the screw shaftof the actuator is directly connected to a rotational part of a motorwithout requiring an additional coupling element.

The present teachings help to enable linear motion due to translationalong the length of a screw, such as a screw having one or more threadedportions (e.g., a helically threaded screw). A rotary motion of thescrew around an axis of rotation generally is converted to a linearmotion of a nut and/or a slider assembly. The screw may have alongitudinal axis, and the screw may be rotated generally about thelongitudinal axis of the screw. For example, the screw may be acomponent of a linear actuator and rotated by a driving force providedby a driver such as a motor (e.g., an electric motor such as a steppermotor, a servo motor, or otherwise). The screw may be made of a metallicmaterial (e.g., steel, stainless steel, copper, brass, bronze, aluminum,aluminum alloy, nickel, nickel alloy, or the like).

The screw may have one or more portions having a thread flank structureand at least one thread crest portion. The thread flank structure mayhave a generally opposing flank. The generally opposing flanks may begenerally flat, arcuate, or a combination thereof, or may have pluralflat and/or arcuate surfaces. The generally opposing flanks may beparallel or at an angle relative to each other (e.g., sloped) and mayterminate at a crest portion that may be flat, pointed, curved, or anycombination thereof. For example, the thread flank structure may includeat least one external helical thread, which may have a sectional profilethat may be generally rectangular, trapezoidal, triangular, acombination of curved and flat portions, or any combination. Suchexternal threads may include a unified national thread, acme thread,national buttress thread, national standard taper pipe thread, ISOmetric thread, any combination thereof, or the like.

The linear actuation screw may be a ball screw. The ball screw mayinclude a ball nut that houses and recirculates balls, rollers,generally rounded or cylindrical units, or other elements. The interfacebetween the linear actuation screw and the ball nut may be made by theballs, rollers, or other elements that roll within the grooves of thethreading of the screw (e.g., the threading of the first end portion ofthe linear actuation screw). The profile the linear actuation screw mayhave a plurality of ball grooves defining the threaded structure of atleast a portion of the screw (e.g., the first end portion). The ballgrooves may be of a shape that receives and guides the balls, rollers,or the like that are recirculated through the ball nut to provide linearmotion. The ball grooves may be generally rounded. The ball grooves mayhave generally rounded or arcuate segments. For example, the ballgrooves may be a gothic arch ball groove.

The linear actuation screw of the present teachings includes anelongated shaft that has a first end portion and a second end portion(e.g., on the opposing side of the elongated shaft, on an opposing sideof a sloping intermediate portion, or both). Between the first endportion and second end portion may be a sloping intermediate portion.The length and diameter of the portions of the linear actuation screwmay be dependent upon the application (e.g., what is being linearlytransferred, the size and power of the motor).

The first end portion of the linear actuation screw may be measured froma terminal end of the linear actuation screw to the area adjacent thesloping intermediate portion. The first end portion may be the longestportion of the linear actuation screw (i.e., longer than the second endportion and longer than the sloping intermediate portion). The first endportion may be configured for advancing a nut, linear slider, or othermoving element along at least a portion of the first end portion. Thefirst end portion of the linear actuation screw may serve as the areaupon which a nut, linear slider, or other moving element is positionedand can translate fore and aft along an axis that is coaxial with orgenerally parallel to the longitudinal axis of the linear actuationscrew.

The first end portion may include a threaded outer wall over at least aportion of its length. The threading may permit balls, rollers, or otherelements, held and recirculated by a ball nut situated on the first endportion, to travel within the grooves (or between flank structures). Thefirst end portion may be threaded only along the portions of the linearactuation screw where a ball nut, a sliding member, or other movingelement is desired to or is permitted to translate. The first endportion may be threaded over only a portion of the first end portion.The first end portion may be threaded over about 50 percent or more ofits length. The first end portion may be threaded over substantially theentire first end portion. The pitch of the threads may be about 0.25 mmor more, about 1 mm or more, about 2 mm or more, or about 3 mm or more.The pitch of the threads may be about 10 mm or less, about 9 mm or less,or about 8 mm or less.

The first end portion may have a threaded outer wall having a generallyconstant first diameter (e.g., as measured from a crest of the one ormore threads surrounding the first end portion), where the firstdiameter is the major diameter, over at least a portion of its length.The first diameter may be about 2 mm or more, about 4 mm or more, orabout 6 mm or more. The first diameter may be about 12 mm or less, about10 mm or less, or about 8 mm or less. The first diameter of the threadedouter wall of the first end portion may be generally constant oversubstantially the entire length of the first end portion. The firstdiameter of the threaded outer wall of the first end portion may begenerally constant over only a portion of the length of the first endportion. The threaded outer wall of the first end portion may have agenerally constant minor diameter (i.e., the smallest material diameterof a screw thread) over at least a portion of its length. The minordiameter of the threaded outer wall of the first end portion may begenerally constant over substantially the entire length of the first endportion.

The first end portion may include a portion that is a different diameterthan the generally constant first diameter (e.g., the major diameter),the generally constant minor diameter, or both. The different diameterportion may be generally unthreaded, generally smooth, or both. Thedifferent diameter portion may be adapted to be supported by a carriageof a linear actuator. For example, a different diameter portion may belocated at the terminal end (i.e., free end) of the first portion. Thedifferent diameter portion may be supported by an end support of acarrier in an actuator assembly. The different diameter portion may bepermitted to rotate within the end support (e.g., via one or morebearings, such as one or more simple end bearings located on or withinthe end support).

A second end portion of the linear actuation screw may be located on theopposing side of the linear actuation screw as the first end portion,located on an opposing side of a sloping intermediate portion, or both.The linear actuation screw may terminate at the end of the second endportion. The second end portion may be configured to be inserted into athrough passage of a motor. The second end portion may be configured toreceive a motor fastening nut around it in order to secure the linearactuation screw to a motor.

The second end portion may include a threaded outer wall over at least aportion of its length. The threading may permit a motor fastening nut tobe threadingly engaged with the second end portion to secure the linearactuation screw within a motor. The second end portion may be threadedover only a portion of the second end portion. The second end portionmay be threaded over about 50 percent or more of its length. The secondend portion may be threaded over substantially the entire second endportion. There may be one or more unthreaded areas between the first endportion and the second end portion.

The second end portion may have a threaded outer wall having a generallyconstant second diameter (e.g., as measured from a crest of the one ormore threads surrounding the second end portion), where the seconddiameter is the major diameter, over at least a portion of its length.The second diameter may be about 2 mm or more, or about 3 mm or more.The second diameter may be about 6 mm or less, or about 5 mm or less.The second diameter may be between about 3 mm and about 5 mm. Forexample, the second end portion may have M4 threads, where M is thenominal outer diameter of the screw in millimeters for ISO metric screwthreads (i.e., 4 mm threaded portions). The second diameter of thethreaded outer wall of the second end portion may be generally constantover substantially the entire length of the second end portion. Thesecond diameter of the threaded outer wall of the second end portion maybe generally constant over only a portion of the length of the secondend portion. The threaded outer wall of the second end portion may havea generally constant minor diameter (i.e., the smallest materialdiameter of a screw thread) over at least a portion of its length. Theminor diameter of the threaded outer wall of the second end portion maybe generally constant over substantially the entire length of the secondend portion. The second end portion may have a generally constant seconddiameter that is different from the first diameter of the first endportion. The second diameter, the minor diameter of the second endportion, or both, may be smaller than the first diameter, the minordiameter of the first end portion, or both.

The linear actuation screw may include a sloping intermediate portionjoining the first end portion and the second end portion. The slopingintermediate portion may be adapted to be received within the throughpassage of the motor of a linear actuation assembly. The slopingintermediate portion may contact one or more of the walls defining thethrough passage of the motor. The walls may defining the through passageof the motor may be rotational elements of the motor. The throughpassage of the motor may include a tapered portion that generallymatches the slope and dimensions of the sloping intermediate portion tomate the linear actuation screw to the motor (i.e., without a couplingjoining the linear actuation screw and a motor shaft).

The sloping intermediate portion may include portions that are threaded.The sloping intermediate portion may be threaded over substantially itsentire length. The sloping intermediate portion may be textured toprovide a frictional surface to reduce slipping of the slopingintermediate portion within a through passage of a motor. Preferably,the sloping intermediate portion may include an outer wall that isgenerally smooth and continuous over at least a portion, over at least amajority, or over substantially the entirety of the area of the outerwall. The sloping intermediate portion may be free of, or substantiallyfree of (e.g., about 10% or less, about 5% or less, or about 2% or lessof the length), threading.

The diameter of the sloping intermediate portion may decrease as itextends from the first end portion toward the second end portion. Theportion of the sloping intermediate portion having the largest diametermay be generally equal to or less than the first diameter (or theaverage first diameter) of the first end portion. The portion of thesloping intermediate portion having the largest diameter may begenerally equal to the minor diameter (or average minor diameter) of thefirst end portion. The portion of the sloping intermediate portionhaving the smallest diameter may be generally equal to or greater thanthe second diameter (or the average second diameter) of the second endportion. The portion of the sloping intermediate portion having thesmallest diameter may be generally equal to the minor diameter (oraverage minor diameter) of the second end portion.

The sloping intermediate portion may have a slope that is measuredrelative to the longitudinal axis of the linear actuation screw. Theslope may be generally constant over a majority of the length of thelinear actuation screw. The sloping intermediate portion may form anangle of about 2 degrees or more, about 4 degrees or more, or about 5degrees or more with the longitudinal axis of the linear actuationscrew. The sloping intermediate portion may form an angle of about 14degrees or less, about 12 degrees or less, about 10 degrees or less, orabout 8 degrees or less. For example, the slope may be about 7 degreesrelative to the longitudinal axis of the linear actuation screw.

The sloping intermediate portion may have a length that is longer thanthe length of the second end portion. The sloping intermediate portionmay have a length that is shorter than the length of the second endportion. The sloping intermediate portion may have a length that isapproximately equal to the length of the second end portion. A ratio ofthe length of the second end portion to a length of the slopingintermediate portion may be about 4:1 to about 0.5:1 (e.g., about 3.3:1to about 0.7:1).

The sloping intermediate portion is preferably integrally formed withthe linear actuation screw. However, it is also contemplated that thesloping intermediate portion can be created on an existing screw via atapered adapter. The tapered adapter may have a generally conical orfrustoconical exterior surface. The tapered adapter may be generallyhollow. The tapered adapter may have a generally constant innerdiameter. The inner diameter may remain fixed before and after assemblywith the screw. The tapered adapter may maintain its shape before andafter assembly with the screw, before and after being inserted into amotor, or both. For example, the tapered adapter may be incapable ofenlarging relative to a longitudinal axis. The tapered adapter may bepositioned over a portion of a linear actuation screw (e.g., over thesecond end portion, adjacent to the first end portion) to provide asloping intermediate portion between a first end portion and a secondend portion. A portion of the linear actuation screw (e.g., the secondend portion) may extend beyond the tapered adapter (e.g., the portion ofthe tapered adapter having the smallest outer diameter). The taperedadapter may serve to provide a strong and/or correct mating between themotor (e.g., the through passage of the motor and the walls defining thethrough passage) and the linear actuation screw.

The linear actuation screw may include one or more interface portions.The interface portion may act as a shoulder of the linear actuationscrew. The interface portion may serve as a stopper (i.e., to inhibitthe linear actuation screw from penetrating the through passage of themotor further). The interface portion may have an outer diameter that islarger than the first diameter of the first end portion, larger than thesecond diameter of the second end portion, or both. The interfaceportion may be a ring or nut around the screw. The interface portion maybe integrally formed with the linear actuation screw. The interfaceportion may be a separate element secured around the liner actuationscrew. The interface portion may be located on the first end portion.The interface portion may be located between the first end portion andthe second end portion of the linear actuation screw.

The linear actuation screw may include one or more features for allowingthe screw to be secured within an assembly. The features may cause thelinear actuation screw to be held in place (e.g., prevented fromrotating) while the linear actuation screw is being installed or securedwithin the motor (e.g., by securing the motor fastening nut to thelinear actuation screw). The linear actuation screw may include one ormore generally flat portions (e.g., wrench flats). The generally flatportions may be located on the first end portion of the linear actuationscrew (e.g., toward the sloping intermediate portion) or between thefirst end portion and the second end portion of the linear actuationscrew. The flat portions may allow the linear actuation screw to begripped (e.g., by a wrench or other clamping device), such as duringinstallation. For example, by gripping the linear actuation screw, thescrew is prevented from rotating while the motor fastening nut is beingthreadingly secured on the second end portion of the linear actuationscrew. The linear actuation screw may include a socket end (e.g., a hexsocket end) located at the terminal end (or the free end) of the firstend portion of the linear actuation screw. The socket end may receive awrench (e.g., a hex key), which may cause the linear actuation screw torotate, or can be used to make the linear actuation screw remain inposition (e.g., not rotate).

The linear actuation screw may include an encoder journal extending fromthe terminal end of the second end portion. The encoder journal mayfunction to be received within an encoder attached to the motor formeasuring rotation of the rotation elements of the motor, rotation ofthe linear actuation screw, or both. The encoder journal may extend awayfrom the second end portion along the longitudinal axis of the linearactuation screw. The encoder journal may be of a sufficient length toextend through the through passage of the motor and beyond the motor(i.e., so that the end of the encoder journal is visible outside of themotor if the encoder was not secured to the motor). The encoder journalmay be integrally formed with the linear actuation screw. The encoderjournal may be part of the screw shaft, so that the encoder journal andthe other portions of the linear actuation screw are made from a singlepiece of material. The encoder journal may be separately attached to thelinear actuation screw. The encoder journal may generally be free ofthreads. The encoder journal may include one or more threaded portionsover a portion or all of its length. The encoder journal may have agenerally constant diameter. The encoder journal may have a diameterthat is generally equal to the second diameter of the linear actuationscrew. Preferably, the encoder journal diameter may be generally lessthan the second diameter of the linear actuation screw (e.g., to allowfor the motor fastening nut to pass over the length of encoder journalto be secured to the second end portion of the linear actuation screw).The encoder journal may have a diameter that is generally larger than orequal to the minor diameter of the second end portion. The encoderjournal may have a diameter that is generally smaller than the minordiameter of the second end portion.

The present teachings contemplate the use of the linear actuation screwas disclosed herein in a motorized assembly. The motorized assembly mayinclude the linear actuation screw and a motor. The motor may include afirst end portion, a second end portion, and a through passage throughwhich the liner actuation screw is adapted to at least partiallypenetrate. The motor may be a stepper motor, a servo motor, or other.The through passage of the motor may extend from the first end portionof the motor through to the opposing second end portion of the motor.The opening of the second end portion of the motor (i.e., defining thethrough passage) may be large enough to allow access to the throughpassage and/or portions of the linear actuation screw (e.g., the secondend portion, the encoder journal, or both). The opening of the secondend portion may be large enough to receive the motor fastening nut. Theopening may have a diameter measuring about 4 mm or more, about 5 mm ormore, or about 6 mm or more. The opening may have a diameter measuringabout 12 mm or less, about 10 mm or less, or about 9 mm or less. Forexample, the opening may have a diameter of about 8 mm. At least aportion of the though passage may be generally tapered (e.g., to receiveand/or engage the sloping intermediate portion). The motor may include acover plate on the first end portion, the second end portion, or both.

The motor may include an encoder secured thereto. For example, anencoder may be clamped or otherwise secured to the second end portion ofthe motor. The encoder may be adapted to receive an encoder journalextending from the second end portion of the linear actuation screw formeasuring the rotation of the screw, the rotation of the rotatingelements of the motor, or a combination thereof.

The present teachings also contemplate a method of assembling amotorized assembly including the linear actuation screw as describedherein. The linear actuation screw may be directly connected to themotor (e.g., the motor rotation portion) by inserting the linearactuation screw at least partially into the through passage of the motorfrom the first end portion. The linear actuation screw may be securedwithin the motor by threadingly engaging a motor fastening nut onto thesecond end portion of the linear actuation screw. The motor fasteningnut may be inserted through the opening defining the through passage atthe second end portion of the motor. The motor fastening nut, having athreaded hollow portion, may receive and engage a portion of the linearactuation screw (e.g., the second end portion). The diameter of thehollow portion of the motor fastening nut may be greater than thediameter of an encoder journal and/or the free end of the linearactuation screw (i.e., at or near the second end portion of the screw)to allow the motor fastening nut to be slid over portions of the screwuntil it can be put into threading engagement with the threaded portionof the second end portion of the linear actuation screw. The slopingintermediate portion of the screw may matingly engage a wall definingthe through passage. Upon securing the linear actuation screw within themotor by threadingly engaging the motor fastening nut onto the secondend portion of the linear actuation screw, it is contemplated that themotor may require no further assembly steps for operation. The motorizedassembly may be free of any adapter or coupling joining the linearactuation screw and the motor.

During operation of the motor, at least a portion of the linearactuation may be exposed. A substantial portion (e.g., a majority) ofthe first end portion of the linear actuation screw may be locatedexternal of the motor and may be free of any enclosure. Other portionsof the linear actuation screw (e.g., the second end portion, the slopingintermediate portion, or both) may be received within and/or concealedby the motor. The motor may include a motor plate (on the first endportion of the motor, the second end portion of the motor, or both) forat least partially enclosing the motor. The linear actuation screw maybe inserted so that the sloping intermediate portion is longitudinallyspaced within the motor at a distance from an outer wall of the motorplate (e.g., about 0.5 mm or more, about 1 mm or more, or about 2 mm ormore; about 6 mm or less, about 5 mm or less, or about 4 mm or less). Itis contemplated, that the space between the sloping intermediate portionand the outer wall of the motor plate may be no greater than a totallength of the sloping intermediate portion.

The linear actuator may include suitable structure for supporting thelinear actuation screw as described herein for rotation. The actuatorassembly may include a carrier that carries the linear, actuation screw.The actuator assembly may include the motor, which drives rotation ofthe linear actuation screw. The actuator assembly may include a linearslider for translating fore and aft along an axis that is generallycoaxial with or generally parallel to the longitudinal axis of thelinear actuation screw.

The carrier may include a first end portion and a second end portion.The first end portion may have at least one end bearing. The first endportion of the carrier may support the first end portion of the linearactuation screw. The second end portion of the carrier may include themotor. The second end portion of the linear actuation screw may beattached directly to the motor and penetrate at least partially into themotor. The motor may include one or more bearings for supporting and/orpermitting rotation of the second end portion within the motor. Therotation portion of the motor may be supported by one or a set ofpreloaded or non-preloaded bearings and/or simple end bearings.

The linear actuator may also have suitable structure for maintaining thelinear slider in a stable position and for allowing the slider totranslate fore and aft in a direction that is generally parallel to orcoaxial with the longitudinal axis of the linear actuation screw. Forexample, the linear actuator may include at least one elongated linearrail having a longitudinal axis, a base, and optionally a pair ofopposing side walls projecting outwardly from the base. The motor orother driver and linear actuation screw may be located between theopposing side walls. The linear actuation screw may be directlyconnected to and secured within the motor or other driver and in drivingrelationship with the motor so that the motor is adapted to rotate thelinear actuation screw generally about the longitudinal axis of thescrew.

The linear slider may include or may be attached to the ball nut of thelinear actuation screw (e.g., the ball nut of a ball screw). The linearslider may have one or more guide structures adapted for engaging a railof the linear actuator. The guide structures may also resist separationof the linear slider from the rail during operation. A guide structuremay slidingly attach the linear slider to the rail, for example by wayof bearings that rollingly engage the rail (e.g., miniature ballbearings, roller bearings, or the like). The bearings may be mounted tothe linear slider, such as at or near an edge of the linear slider or atsome other location on the linear slider.

The assembly may be free of an intermediate support unit between themotor and the at least one end bearing (at the first end portion of thecarrier). The assembly may be free of an adapter or coupling joining thelinear actuation screw to a motor shaft (e.g., a rotational shaft of themotor). The assembly may be free of a motor bracket joining the motor tothe carrier. The absence of any, all, or a combination of these featuresmay permit the footprint of the carrier to be smaller than a traditionallinear actuator assembly. The present teachings contemplate the carrierhaving an overall length. The linear actuation screw has a travel lengthover the distance which a screw nut and/or a linear slider located onthe linear actuation screw can travel. The ratio of the overall lengthof the carrier to the travel length of the linear actuations crew may beabout 1.4:1 or less (e.g., about 1.3:1 or less). The actuator assemblymay result in a reduction of overall length of at least 15%, at least20%, or more, as compared with a tradition structure (e.g., a structurehaving an intermediate support unit, a motor bracket, and/or acoupling).

Turning now to the figures, FIG. 1 illustrates a traditional linearactuator assembly. The traditional assembly 100 includes an end support110 at one end and a motor bracket 104 and a motor 120 at the opposingend. A linear rail 116 extends along at least a portion of the length ofthe assembly 100. The motor bracket 104 attaches the motor 120 to thelinear rail 116 of the assembly 100. A screw 112 is supported at one endby the end support 110 and by an intermediate support unit 108 towardthe opposing end of the screw. The intermediate support unit 108 alsoincludes preloaded rolling bearings (not shown) for supporting screwshaft rotation movement and for taking the axial load. A linear slider114 travels along the length of the screw 112 and is also supported bythe linear rail 116. The screw 112 is joined to the motor 120 (i.e., themotor shaft of the motor) via a coupling 106. Therefore, the traditionalassembly 100 has three rotational parts: the shaft in the motor 120, theshaft of the screw 112, and the coupling 106 connecting them. Theoverall length of the traditional assembly is shown as L_(overall). Thelength the linear slider 114 is permitted to travel along the screw 112is shown as L_(travel).

FIG. 2 illustrates a linear actuation screw 20 of the present teachings.The linear actuation screw 20 has an elongated shaft 22 which has alongitudinal axis LA. The linear actuation screw 20 rotates about thelongitudinal axis LA, and rotation of the linear actuation screw 20 isdriven by a motor 50. The linear actuation screw 20 has a first endportion 24, which is generally exposed (i.e., not concealed by the motor50). The linear actuation screw 20 as illustrated is a ball screw andalso includes a ball nut 38. To engage with the motor 50, the second endportion 30 and sloping intermediate portion 34 (see FIGS. 3A and 3B) ofthe linear actuation screw 20 are inserted into the first end portion ofthe motor 52. The motor 50 has an opposing second end portion 58. Thethreading of the linear actuation screw has been omitted for clarity ofthe remainder of the figure.

FIGS. 3A and 3B illustrate a linear actuation screw 20 of the presentteachings. FIGS. 3A and 3B illustrate a portion of the first end portion24 of the linear actuation screw 20, which has a threaded outer wall 26.The first end portion 24 has a generally constant diameter D1 asmeasured from the crests of the threaded outer wall 26. On the opposingend of the linear actuation screws 20 are a second end portion 30,having a threaded outer wall 32. The second end portion 30 has agenerally constant diameter D2, as measured from the crests of thethreaded outer wall 32, which is smaller than the generally constantdiameter D1 of the first end portion 24 of the linear actuation screw20. The linear actuation screw 20 includes a sloping intermediateportion 34 located between the first end portion 24 and the second endportion 30. The slope of sloping intermediate portion 34 may be measuredin degrees by the angle α formed between a plane extending generallyalong and beyond the sloping intermediate portion 34 and thelongitudinal axis LA of the linear actuation screw 20. As illustrated inFIGS. 3A and 3B, the sloping intermediate portion 34 is free ofthreading and may be generally smooth. The portion of the slopingintermediate portion 34 having the largest diameter, shown here wherethe sloping intermediate portion 34 connects to the first end portion24, may be generally the same diameter as the generally constantdiameter D1 of the first end portion 24, as shown in FIG. 3B. Thelargest diameter portion of the sloping intermediate portion 34 may besmaller than the generally constant diameter D1 of the first end portion34, as shown in FIG. 3A.

FIG. 4 is a partial cutaway view of a linear actuation screw 20 receivedwithin a through passage 56 of a motor 50. As shown in FIG. 2, thelinear actuation screw 20 is inserted into the through passage 56 at thefirst end portion 52 of the motor 50. The through passage 56 is shapedin such a way to accommodate the sloping intermediate portion 34 of thelinear actuation screw 20. The linear actuation screw 20 is securedwithin the motor 50 by a motor fastening nut 40 that is in threadingengagement with the second end portion 30 (i.e., at the threaded outerwall 32 as shown in FIGS. 3A and 3B).

FIG. 5 illustrates a longitudinal cross section of a linear actuationscrew 20 having a sloping intermediate portion 34 by way of a taperedadapter 36. The tapered adapter 36 has a constant inner diameter and ispositioned upon the linear actuation screw 20. The motor fastening nut40 is then secured on the second end portion 30 of the linear actuationscrew 20 to secure the linear actuation screw within the motor (notshown). The tapered adapter 36 may provide a sloping intermediateportion 34 forming an angle α (as shown in FIGS. 3A and 3B) with thelongitudinal axis LA of the linear actuation screw 20.

FIGS. 6A, 6B and 6C illustrate a linear actuation screw 20 having anencoder journal 42 extending from the second end portion 30. FIG. 6Aillustrates the linear actuation screw 20 extending into a motor 50. Themotor 50 includes a through passage 56 for receiving a portion of thelinear actuation screw 20. The through passage 56 extends from the firstend portion 52 of the motor 50 through the second end portion 58 of themotor 50 on the opposing side. The encoder journal 42 extending from thelinear actuation screw 20 extends beyond the second end portion 58 ofthe motor 50 to be received within an encoder 62 (FIG. 6C) for measuringrotation, which is attached to the second end portion 58 of the motor50. FIG. 6B illustrates the linear actuation screw 20 of FIG. 6A withthe motor omitted. As shown, the motor fastening nut 40 is threadinglyengaged with the second end portion 30 of the linear actuation screw 20for securing the screw within the motor. The encoder journal 42 extendsfrom the second end portion 30 of the screw. The linear actuation screw20 of FIG. 6C illustrates a different diameter portion 28 than thediameter of the rest of the first end portion 24. The different diameterportion is adapted to be supported by a first end portion 74 of acarrier 72 within an actuator assembly 70 (see FIG. 7).

FIG. 7 illustrates an exemplary actuator assembly 70 of the presentteachings. The actuator assembly includes a linear actuation screw 20supported by a carrier 72. The first end portion of the linear actuationscrew 20 is supported by a first end portion 74 of the carrier 72. Theopposing end of the linear actuation screw (i.e., the slopingintermediate portion and the second end portion as shown in FIGS. 3A and3B) is inserted into the motor 50. The motor 50 includes a motor plate54. The carrier 72 includes a linear rail 80, which extends between thefirst end portion 74 of the carrier 72 and the motor 50. A linear slider78 (positioned on or including the ball nut 38 as shown in FIG. 2)translates fore and aft along the length of the linear actuation screw20 and is further supported by the linear rail 80. The overall length ofthe actuator assembly 70 is shown as L_(overall). The length the linearslider 78 is permitted to travel along the linear actuation screw 20 isshown as L_(travel). As seen when comparing with the traditionalassembly of FIG. 1, the ratio of L_(overall) to L_(travel) is improved,providing a smaller difference between the L_(overall) and L_(travel) inthe exemplary actuator assembly 70 of the present teachings.

Among other differences relative to prior technologies, the teachingsenvision linear actuators that are free of a coupling joining the screwshaft to a motor shaft; an intermediate support unit between the firstend portion of the carrier and the motor; a motor bracket joining themotor to the assembly; or any combination thereof.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

Any numerical values recited herein include all values from the lowervalue to the upper value in increments of one unit provided that thereis a separation of at least 2 units between any lower value and anyhigher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to N,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which are lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

Unless otherwise stated, all ranges include both endpoints and allnumbers between the endpoints. The use of “about” or “approximately” inconnection with a range applies to both ends of the range. Thus, “about20 to 30” is intended to cover “about 20 to about 30”, inclusive of atleast the specified endpoints.

The disclosures of all articles and references, including patentapplications and publications, are incorporated by reference for allpurposes. The term “consisting essentially of” to describe a combinationshall include the elements, ingredients, components or steps identified,and such other elements ingredients, components or steps that do notmaterially affect the basic and novel characteristics of thecombination. The use of the terms “comprising” or “including” todescribe combinations of elements, ingredients, components or stepsherein also contemplates embodiments that consist essentially of, oreven consisting of, the elements, ingredients, components or steps.

Plural elements, ingredients, components or steps can be provided by asingle integrated element, ingredient, component or step. Alternatively,a single integrated element, ingredient, component or step might bedivided into separate plural elements, ingredients, components or steps.The disclosure of “a” or “one” to describe an element, ingredient,component or step is not intended to foreclose additional elements,ingredients, components or steps.

Relative positional relationships of elements depicted in the drawingsare part of the teachings herein, even if not verbally described.Further, geometries shown in the drawings (though not intended to belimiting) are also within the scope of the teachings, even if notverbally described.

What is claimed is:
 1. A linear actuation screw comprising an elongatedshaft having a first end portion, a second end portion on an oppositeside of the elongated shaft as the first end portion, and a slopingintermediate portion between the first end portion and the second endportion, wherein: 1a) the first end portion has a threaded outer wallhaving a generally constant first diameter as measured from a crest overat least a portion of its length and is configured to advance a nut or asliding member along at least a portion of the first end portion; 1b)the second end portion has a threaded outer wall having a generallyconstant second diameter that is different from the first diameter andis configured to receive a motor fastening nut around it in order tosecure the linear actuation screw to a motor; and 1c) the slopingintermediate portion includes an outer wall that is generally smooth andcontinuous over at least a majority of the area of the outer wall;wherein rotation of the linear actuation screw is adapted to be drivenby a motor.
 2. The linear actuation screw of claim 1, wherein: 2a) thefirst diameter of the threaded outer wall of the first end portion isgenerally constant over substantially the entire length of the first endportion; 2b) the second diameter of the threaded outer wall of thesecond end portion is generally constant over substantially the entirelength of the second end portion; or both 2a) and 2b).
 3. The linearactuation screw of claim 1, wherein: 3a) the threaded outer wall of thefirst end portion is threaded over only a portion of the first endportion; 3b) the threaded outer wall of the second end portion isthreaded over only a portion of the second end portion: or both 3a) and3b).
 4. The linear actuation screw of claim 1, wherein: 4a) the threadedouter wall of the first end, portion is threaded over greater than 50percent of the length of the first end portion; 4b) the threaded outerwall of the second end portion is threaded over greater than 50 percentof the length of the second end portion; or both 4a) and 4b).
 5. Thelinear actuation screw of claim 1, wherein a portion is unthreadedbetween the first end portion and the second end portion.
 6. The linearactuation screw of claim 1, wherein an average first diameter of thefirst end portion as measured from a trough is different from an averagesecond diameter of the second end portion as measured from a trough. 7.The linear actuation screw of claim 1, wherein the sloping intermediateportion has a slope between about 5 degrees and about 10 degreesrelative to a longitudinal axis of the linear actuation screw.
 8. Thelinear actuation screw of claim 7, wherein the sloping intermediateportion has a generally constant slope over a majority of its length. 9.The linear actuation screw of claim 1, wherein a ratio of the length ofthe second end portion to a length of the sloping intermediate portionis about 3.3:1 to about 0.7:1.
 10. The linear actuation screw of claim1, wherein the linear actuation screw is adapted to penetrate through anopening at a first end portion of the motor at least partially through athrough passage of and be secured.
 11. The linear actuation screw ofclaim 10, wherein an encoder journal is located at and extends from thesecond end portion of the linear actuation screw along the longitudinalaxis of the linear actuation screw for receipt within an encoder securedto a second portion of the motor opposite the first end portion of themotor.
 12. The linear actuation screw of claim 1, wherein the linearactuation screw is a ball screw.
 13. An actuator assembly comprising: i)a linear actuation screw comprising: an elongated shaft having a firstend portion, a second end portion on an opposite side of the elongatedshaft as the first end portion, and a sloping intermediate portionbetween the first end portion and the second end portion, wherein: thefirst end portion has a threaded outer wall having a generally constantfirst diameter as measured from a crest over at least a portion of itslength and is configured to advance a nut of a sliding member along atleast a portion of the first end portion; the second end portion has athreaded outer wall having a generally constant second diameter that isdifferent from the first diameter and is configured to receive a motorfastening nut around it in order to secure the linear actuation screw toa motor; and the sloping intermediate portion includes an outer wallthat is generally smooth and continuous over at least a majority of thearea of the outer wall; ii) a carrier that carries the linear actuationscrew; iii) a motor that drives rotation of the linear actuation screw,and iv) a linear slider for translating fore and aft along an axis thatis generally parallel to the longitudinal axis of the linear actuationscrew.
 14. The actuator assembly of claim 13, wherein the carrierincludes a first end portion and a second end portion, the first endportion having at least one end bearing and supporting the first endportion of the linear actuation screw; the second end portion includingthe motor; and wherein the second end portion of the linear actuationscrew is attached directly to the motor and penetrates at leastpartially into the motor.
 15. The actuator assembly of claim 13, whereinthe carrier includes a linear rail upon which the slider translates foreand aft.
 16. The actuator assembly of claim 13, wherein the assembly isfree of an intermediate support unit having preloaded bearings forsupporting screw shaft rotation movement between the motor and the atleast one end bearing.
 17. The actuator assembly of claim 13, whereinthe assembly is free of a) a motor bracket joining the motor to thecarrier; b) an adapter or coupling joining the linear actuation screwand the motor; or is free of both of a) and b).
 18. The actuatorassembly of claim 13, wherein the linear actuation screw is a ballscrew.
 19. The actuator assembly of claim 13, wherein the carrier has anoverall length, and wherein the linear actuation screw has a travellength over the distance which a screw nut located on the linearactuation screw can travel; and wherein a ratio of the overall length ofthe carrier to the travel length of the linear actuation screw is about1.4:1 or less and about 1:1 or greater.
 20. The actuator assembly ofclaim 13, wherein the actuator assembly results in a reduction ofoverall length of at least 15% as compared with a traditional linearactuator assembly having an end support at one end, a motor bracket anda motor at an opposite end, a screw joined to the motor via a coupling,and an intermediate support unit having preloaded rolling bearings forsupporting screw shaft rotation movement.